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Programming Fundamentals

Programming


  • programming is simply instructions for a computer to follow
  • programming languages at their most basic level have 2 things: ways to store data, ways to manipulate data
  • the order in which data is manipulated is called flow
  • and the structures that determine that order are called control flow structures

A quick and dirty intro


We will cover:
  • variables
  • conditional statements
  • loops
  • functions

There is a LOT more to programming than the above.

where

  • irb: in terminal (in any folder), type irb
  • rails console: within a rails app folder, in terminal, type rails console
  • codecademylabs: labs.codecademy.com
  • .rb files: create a .rb file and then type ruby <file.rb> in terminal

output


logging things to the console is a good way to check your variables.

in ruby, we log things by using the word puts

Example:

    myVariable = 345
    puts myVariable

    >> 345

Variables


Variables "store" data. 
Variables are ways to talk about data abstractly.

i.e. 
3 + 2 = 5, or 

x = 3
x + 2 = 5

VARiables


Variables have different types.

...some are familiar:

string = any set of characters
integer = whole numbers 

Arrays


An array is a list of variables.

myArray = [variable1, variable2]

it can hold many types of variables or data

myVariable = 4
myArray = [myVariable, "hello", 38578]

you can even have arrays of arrays

Arrays


to get a value from an array you use this notation:

myArray[#], where # is the index of the array

example:
myArray = ['a','b','c', 'd', 'e', 'f']
myArray[0]  #=> 'a'
myArray[4]  #=> 'e'

Array practice


myArray = ['cat','dog','pig','horse','spider']

myArray[0]= ?
myArray.last = ?
myArray.first = ?
myArray[3] = ?

'dog' = ?
'spider' = ?
'horse' = ?

array functions


http://ruby-doc.org/core-1.9.3/Array.html


  • first/last returns first or last item in the array
  • length returns the length of the array
  • sort put the array in order (alphabetically or numerically)
  • reverse returns a new array in the reverse order
  • reverse! returns the same array in the reverse order

Array practice


myArray = ['cat','dog','pig','horse','spider']

myArray.sort = ?
myArray.sort! = ?
myArray.reverse = ?
myArray.reverse! = ?
myArray.length = ?

objects


Objects are just like Arrays except instead of numbers they have "keys" that have names (strings).

e.g.

myObject = { name: "Ashley",
                             age: 26,
                             email: "heyashleyashley@gmail.com" }

object practice


Create an object called 'myObject' for yourself that includes your name, age, and email address

conditional statements


We are going to want to be able to compare values. To do so we use conditional statements.

    ==    are they equivalent?
    >=    greater than or equal
    <=    less than or equal
    !=     not equal

conditional statments


We can use conditional statements in structures to control how/if often a piece of code is run.

These are called control flow structures:
  • if and unless statements
  • for loops
  • while loops
  • case statements

if and unless


if (something) then
    do this
else
    do this
elsif
    do this
end

do this if something

do this unless something

if and unless practice


if a number is greater than or equal to 5, subtract 1, otherwise add 2

if the word is 'hello' print it to the screen, otherwise print the word 'goodbye'

add 2 to a number unless that number = 10

for loops


for i in 1..5
     do something
end

(1..5).each do |n|
     puts n
end

for loop practice


  • Print the number 1-100
  • Print all the letters of the alphabet
  • Create an array with 5 words and print them all out


  • Create an array with 5 words and only print the words that start with the letter 's'

case statements

myARRAY = ["fruit", "meat", "dairy", "veggie"]
myFood = myARRAY[rand()*myARRAy.length]

case myFood
     when "fruit"
            do something
     when "meat"
             do something
end

Case practice


  1. Create an array with the words "colors", "shapes", "numbers"
  2. Create an array for each of those words with at least 3 elements in it
  3. Randomly select a word from your first array
  4. Write a case statement that will randomly select a word from the respective array

e.g. if colors if chosen, select a color from the colors array

fizzbuzz


FizzBuzz is a classic interview question for developers:

Write a program that prints the numbers between 1-100
But for multiples of 3, print Fizz, instead of the number
and for multiples of 5 print Buzz
If the number is a multiple of 3 AND 5, print FizzBuzz

http://c2.com/cgi/wiki?FizzBuzzTest

more problems


resources


functions


functions are way to store a block of code that you want to reuse

    def functionName(parameters)
         do something
    end

 you call a function by typing it's name:
funcitonName(params)
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